Maximising the potential for bacterial phenotyping using time‐of‐flight secondary ion mass spectrometry with multivariate analysis and Tandem Mass Spectrometry

Abstract

The increasing trend towards bacteria becoming resistant to current antibiotic treatments is of great concern to the healthcare industry with severe potential consequences for society as a whole. In many cases, it is the interaction of the antibacterial agent with the targets within the bacterial envelope of the microorganism that is a critical factor. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is uniquely capable of probing the chemistry in this region. This study aimed at optimising sample preparation and data pre-processing for bacterial analysis with ToF-SIMS and principal components analysis to study small chemical differences related to changes in bacterial phenotype that will help to find new antibiotics and understand how antibiotics are trafficked in the bacteria. ToF-SIMS analysis was performed using a J105 instrument equipped with a 40 kV C 60 + ion source. Combination of positive and negative ion mode data enhanced the multivariate model quality regarding classification and aided chemical identification particularly when coupled with tandem mass spectrometry.

Improved Molecular Imaging in Rodent Brain with Time-of-Flight-Secondary Ion Mass Spectrometry Using Gas Cluster Ion Beams and Reactive Vapor Exposure

“…29,30 A series of principal components are calculated based on the variation between the spectra in the dataset. The largest variance is captured in the first principal component (PC1).…”

Benefits of NaCl addition for time‐of‐flight secondary ion mass spectrometry analysis including the discrimination of diacylglyceride and triacylglyceride ions

“…MS/MS was performed using the J105 as described and demonstrated previously. 2,6,7,20 Briefly, MS/MS was performed in a ToF-ToF configuration with collision-induced dissociation occurring in a short field-free region between the buncher and the reflectron mass analyser where nitrogen gas was injected. Precursor ions have energies in the range 0.5-5 keV depending on their position in the buncher when the bunching voltage was applied.…”

“…Advances in the mass analyser technology featured with SIMS instruments, either new types of ToF configuration or hybrid instruments incorporating analysers normally associated with other types of MS, have improved mass accuracy to several ppm or better – compared with around 150 ppm for large molecular peaks with conventional SIMS instruments . MS/MS capabilities are now also available for several types of SIMS instruments with numerous studies appearing in the literature . However, due to the high cost of replacing or upgrading SIMS instruments, the majority of the community is reliant on conventional systems where the complexity of biological samples combined with the complexity of imaging spectra makes peak identification difficult.…”

“…5 MS/MS capabilities are now also available for several types of SIMS instruments with numerous studies appearing in the literature. [6][7][8][9] However, due to the high cost of replacing or upgrading SIMS instruments, the majority of the community is reliant on conventional systems where the complexity of biological samples combined with the complexity of imaging spectra makes peak identification difficult. In order to meet the demands associated with biological/clinical analysis, it is important that complex mass spectrometric data are accurately interpreted.…”

Latest applications of 3D ToF-SIMS bio-imaging

“…Analysis of bacterial surfaces is important to study drug resistance and bacterial persistence and remains a popular target for SIMS analysis with secreted signaling/sensing molecules being recently detected. 27,28 One of the first true 3D imaging examples of a biological specimen was the analysis a frog egg using C 60 as both the analysis and the etching beam. The frog egg was very large (approximately 1.2 mm diameter) compared to usual SIMS samples and as such the entire egg was not analyzed.…”